3.16 Popliteal Fossa Block

Question 1

Describe Region supplied by nerves arising from the popliteal fossa

Answer 1

1. Tibial
   Medial

Main terminal branch sciatic

Sensory branches

1. Sural N arises in pop fossa
   - ->lateral border of foot
2. Medial Plantar N
   Arises @ flexor retinac
   Supplies medial 2/3 sole foot
   Plantar medial 3.5 toes
3. Lateral Plantar N.
   Flex Ret
   Supply lateral 1/3 sole foot
   plantar 1.5 toes

Question 2

Popliteal Fossa N and Cutaneous Distribution

Answer 2

Peroneal - Lateral

Common Peroneal N:

Branch <- sciatic N
@ vary distance above pop fossa

Divides into deep + superficial peroneal N

Sensory Branches:

1. Sural comm N
   absent 20%
   Join Sural N
2. Superficial Peroneal N
   lower outer aspect lower leg
   Terminal branches innervate dorsum foot
3. Deep Peroneal N.
   1st webspace

Question 3

What motor response would you get stimulating popliteal fossa N

Answer 3

Tibial N:
Plantar flexion toes
Inversion foot

CPN:
Dorsiflexion toes
Foot eversion

Sciatic:
Combo

Isolate calf twitch
Direct stim of sciatic branches to Gastroc
Not signify correct needle tip

Question 4

Technique

Answer 4

Standard preop assessment and slimrag

Awake and able
1. Prone
flexion extension will aid ID of crease

2. Asleep / pain
   Supine leg raised by assistant
   Lateral
3. Palpate
   Tendon bicep fem -lateral
   Semimembranosus - medial

Question 5

Technique

Answer 5

1. Locate intended gap + mark site
   6-8cm prox to mid pop skin crease
2. Needle introduced perpendicular to skin
   advance until foot stim obtained

3. Failure ID twitch
More lateral position nerve trunk
redirect laterally
withdrawal 
Or re-puncture 1cm more laterally

4. Injection of LA after negative aspiration